Dynamics simulation of pulsed-DC helium plasma jet enhanced by an additional floating electrode

A two-dimensional axisymmetric self-consistent fluid model was established using COMSOL Multiphysics to investigate the dynamics behavior of pulsed-DC helium plasma jet enhanced by an additional floating electrode. Comparative analysis of the Laplacian electric field without and with the floating electrode shows that the floating electrode allows for an intensified electric field inside the tube, which gives rise to the higher number density of electrons and ions before the formation of plasma sheath in the initial stage of streamer development. Subsequently, with the floating electrode applied, the increase of surface charge density in the early stage of streamer development raises the ion flux to the dielectric wall and reduces the sheath potential, finally resulting in the growth of electron energy in the plasma sheath and the electron number density in the plasma channel, before the plasma jet is ejected from the tube. When the plasma jet runs out of the tube, the floating electrode leads to the remarkable improvement of the energy deposition and the significant enhancement of the deposited power, which effectively elevates the electric field and the electron energy in the streamer head. Accordingly, the accelerated impact ionization and promoted streamer propagation increase the number densities of various species and extend the jet length in the later stage of streamer development.